Earth science 5

Exogenic Processes

External processes occurring at Earth's surface due to agents like wind, water, ice, and gravity.

Weathering

The breaking down of rocks into smaller pieces without moving them.

Mechanical Weathering

Physical breakdown of rocks without changing chemical composition.

Chemical Weathering

Rock minerals change due to chemical reactions such as oxidation and hydrolysis.

Biological Weathering

Breakdown of rocks by living organisms like plants, animals, and microbes.

Erosion

Transport of weathered material by water, wind, ice, or gravity.

Mass Wasting

Downhill movement of rock or soil under the influence of gravity.

Types of Mass Wasting

Falls, slides, flows, and creep caused by gravity pulling materials down a slope.

Deposition

Process where sediments transported by erosion settle in a new location.

Movement of Magma

Magma chambers store magma which can evolve before erupting.

Magma Chambers

Storage areas where magma accumulates and evolves before eruption.

Intrusive Pathways

Magma cools and solidifies below Earth's surface forming intrusive igneous rocks.

Extrusive Pathways

Magma reaches the surface forming extrusive igneous rocks like basalt, andesite, rhyolite.

Basaltic Magma

Low silica (45-55%), high iron and magnesium, very fluid; forms shield volcanoes and basalt plateaus.

Andesitic Magma

Intermediate silica (55-65%), more viscous; associated with stratovolcanoes and volcanic arcs.

Volcanic Activity

Effusive and explosive eruptions.

Effusive Eruptions

Low-viscosity magma flows out forming lava flows and broad shield volcanoes.

Explosive Eruptions

High-viscosity magma traps gases causing pyroclastic flows, ash falls, forming stratovolcanoes or calderas.

Stratovolcanoes

Alternating layers of lava and pyroclastic material; formed from explosive and effusive eruptions.

Shield Volcanoes

Formed by low-viscosity basaltic lava that flows widely.

Calderas

Large basin-shaped depressions formed when a volcano collapses after massive eruption.

Magmatic Differentiation

Changes in magma composition as it cools or mixes.

Fractional Crystallization

Early-forming minerals crystallize and settle, altering remaining melt composition.

Assimilation

Magma incorporates surrounding rock material, forming hybrid magmas.

Magma Mixing

Magmas from different sources mix, forming new magma with intermediate properties.

Metamorphism

Changes in mineral components and texture of rocks due to heat, pressure, and fluids.

Contact Metamorphism

Rocks heated by nearby magma or lava, forming non-foliated rocks like hornfels.

Regional Metamorphism

Large-scale tectonic processes involving high pressure and temperature, forming foliated rocks like schist and gneiss.

Dynamic Metamorphism

Mechanical deformation along fault zones, creating rocks like mylonite.

Temperature

Causes minerals to recrystallize forming new stable minerals.

Pressure

Leads to mineral alignment forming foliated textures.

Chemically Active Fluids

Introduce or remove elements, facilitating new mineral growth.

Crustal Deformation

Changing Earth's surface caused by tectonic forces accumulating in the crust.

Deformation

Bending, tilting, and breaking of Earth's crust in response to stress.

Isostasy

Gravitational and buoyant equilibrium between lithosphere and asthenosphere.

Temperature

High temperatures make rocks ductile; low temperatures make them brittle.

Pressure

High pressure leads to plastic deformation; low pressure favors fracturing.

Rock Composition

Sedimentary rocks deform plastically; igneous rocks tend to fracture.

Time

Deformation can be gradual (creep) or sudden (earthquakes).

Stress vs Strain

Stress: force applied per unit area; Strain: deformation from stress.

Compressional Stress

Squeezes rocks, causing shortening and thickening; linked with folding and reverse faults.

Tensional Stress

Pulls rocks apart, causing lengthening; linked with normal faults.

Shear Stress

Causes rocks to slide past each other horizontally; linked with strike-slip faults.

Elastic Strain

Temporary, reversible; rocks return to original shape.

Plastic Strain

Permanent deformation without fracturing.

Brittle Strain

Permanent change with fracturing or breaking.

Folding

Bending of rocks due to compressional forces.

Fold Parts

Limbs, axis, axial plane.

Anticline

Upward-arching fold with oldest rocks at core.

Syncline

Downward-arching fold with youngest rocks at core.

Monocline

Fold in one direction; limbs mostly horizontal.

Faulting

Breaking and movement of rocks due to stress.

Normal Fault

Hanging wall moves down relative to footwall; caused by tension. Example: Great Rift Valley.

Reverse Fault

Compression causes hanging wall to move up; thrust fault is low-angle reverse. Example: Alps.

Strike-Slip Faults

Rocks slide horizontally past each other due to shear. Example: Philippine Fault System.

Plate Tectonics

The motion of Earth's lithosphere plates shaping the surface.

Crust

Outermost solid layer, 5-70 km thick; silicate rocks.

Mantle

2900 km thick; solid/semi-solid, rich in magnesium and iron.

Outer Core

2200 km thick; molten iron and nickel.

Inner Core

1200 km thick; solid iron and nickel.

Lithosphere

Rigid outer layer, crust + upper mantle, divided into tectonic plates.

Asthenosphere

Semi-fluid upper mantle below lithosphere, allows plate movement.

Tectonic Plates

Massive lithosphere slabs covering Earth's surface.

Continental Drift Theory

Proposed by Alfred Wegener (1912); continents were once Pangaea.

Fossil Evidence

Identical fossils (Mesosaurus, Glossopteris) found on distant continents.

Geological Evidence

Matching rock formations and mountain ranges across continents.

Climate Evidence

Glacial deposits and coal deposits indicate past positions.

Fit of Continents

Continental coastlines fit like a puzzle.

Seafloor Spreading

New oceanic crust forms at mid-ocean ridges; plates move outward.

Mid-Ocean Ridges

Underwater mountain ranges where magma rises and forms new crust.

Magma Upwelling

Magma rises through rift valley due to mantle convection.

Formation of New Crust

Magma cools forming new basaltic crust.

Lateral Movement

New crust pushes older crust outward, spreading ocean floor.

Symmetrical Pattern

Magnetic stripes on ocean floor record field reversals symmetrically.

Evidence of Seafloor Spreading

Magnetic stripes, age of rocks, heat flow.

Magnetic Stripes

Record Earth's magnetic reversals symmetrically.

Age of Rocks

Younger at ridges, older at edges; confirmed by radiometric dating.

Heat Flow

Higher at ridges, decreases outward.

Convergent Boundaries

Plates move toward each other; form trenches, mountains, volcanoes.

Oceanic-Continental Convergence

Denser oceanic subducts beneath continental; features: trenches, volcanic arcs. Example: Andes Mountains.

Oceanic-Oceanic Convergence

One oceanic plate subducts under another; features: trenches, island arcs. Example: Mariana Trench.

Continental-Continental Convergence

Continents collide forming mountains; features: high ranges, earthquakes. Example: Himalayas.

Divergent Boundaries

Plates move apart; new crust forms; features: rift valleys, mid-ocean ridges.

Transform Boundaries

Plates slide past each other horizontally; crust neither created nor destroyed.

Impact of Plate Tectonics

Earthquakes, volcanic activity, mountain building, ocean basin formation.

Geological Features

Folds, faults, trenches, volcanoes, rift valleys, mountain ranges.